---
id: CVE-2026-31684
title: 'net: sched: act_csum: validate nested VLAN headers'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: sched: act_csum: validate nested VLAN headers

  tcf_csum_act() walks nested VLAN headers directly from skb->data when an
  skb still carries in-payload VLAN tags. The…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 <
    0410c619e86551677fb79887a38eccad3f5a0725
  - >-
    Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 <
    886469b6455611a511aa6013e957e15e50577513
  - >-
    Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 <
    46c07ad50fa2f4ba7663ee1b72b75ad7ad45cf09
  - >-
    Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 <
    eb3765b90eb8f2a3d6310a80c14a9e57ec4267a2
  - >-
    Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 <
    a69738efea0996d05a3c7d2178551b891744df1b
  - >-
    Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 <
    ec4930979b3f7bbeb7af5744599fc6603a4dba62
  - >-
    Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 <
    3d165d975305cf76ff0b10a3c798fb31e5f5f9a5
  - >-
    Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 <
    c842743d073bdd683606cb414eb0ca84465dd834
  - Linux 3764bfae5056e95617b6ee074129297e11710886
  - Linux >= 4.19.99 < 4.20
  - Linux 5.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T15:24:14.457468Z'
published: '2026-04-25'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T15:32:22.781Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31684'
references:
  - url: 'https://git.kernel.org/stable/c/0410c619e86551677fb79887a38eccad3f5a0725'
  - url: 'https://git.kernel.org/stable/c/886469b6455611a511aa6013e957e15e50577513'
  - url: 'https://git.kernel.org/stable/c/46c07ad50fa2f4ba7663ee1b72b75ad7ad45cf09'
  - url: 'https://git.kernel.org/stable/c/eb3765b90eb8f2a3d6310a80c14a9e57ec4267a2'
  - url: 'https://git.kernel.org/stable/c/a69738efea0996d05a3c7d2178551b891744df1b'
  - url: 'https://git.kernel.org/stable/c/ec4930979b3f7bbeb7af5744599fc6603a4dba62'
  - url: 'https://git.kernel.org/stable/c/3d165d975305cf76ff0b10a3c798fb31e5f5f9a5'
  - url: 'https://git.kernel.org/stable/c/c842743d073bdd683606cb414eb0ca84465dd834'
tags:
  - cve.org
epss: 0.00117
epssPercentile: 0.01668
ingestedAt: '2026-11-06T15:54:04.047Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

net: sched: act_csum: validate nested VLAN headers

tcf_csum_act() walks nested VLAN headers directly from skb->data when an
skb still carries in-payload VLAN tags. The current code reads
vlan->h_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without
first ensuring that the full VLAN header is present in the linear area.

If only part of an inner VLAN header is linearized, accessing
h_vlan_encapsulated_proto reads past the linear area, and the following
skb_pull(VLAN_HLEN) may violate skb invariants.

Fix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and
pulling each nested VLAN header. If the header still is not fully
available, drop the packet through the existing error path.

## Affected

- `Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 < 0410c619e86551677fb79887a38eccad3f5a0725`
- `Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 < 886469b6455611a511aa6013e957e15e50577513`
- `Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 < 46c07ad50fa2f4ba7663ee1b72b75ad7ad45cf09`
- `Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 < eb3765b90eb8f2a3d6310a80c14a9e57ec4267a2`
- `Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 < a69738efea0996d05a3c7d2178551b891744df1b`
- `Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 < ec4930979b3f7bbeb7af5744599fc6603a4dba62`
- `Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 < 3d165d975305cf76ff0b10a3c798fb31e5f5f9a5`
- `Linux >= 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 < c842743d073bdd683606cb414eb0ca84465dd834`
- `Linux 3764bfae5056e95617b6ee074129297e11710886`
- `Linux >= 4.19.99 < 4.20`
- `Linux 5.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.